USACO 2019 US Open Contest, Bronze Problem 1 Bucket Brigade
A fire has broken out on the farm, and the cows are rushing to try and put it out!
The farm is described by a 10×1010×10 grid of characters like this:
.......... .......... .......... ..B....... .......... .....R.... .......... .......... .....L.... ..........
The character 'B' represents the barn, which has just caught on fire. The 'L' character represents a lake, and 'R' represents the location of a large rock.
The cows want to form a "bucket brigade" by placing themselves along a path between the lake and the barn so that they can pass buckets of water along the path to help extinguish the fire. A bucket can move between cows if they are immediately adjacent in the north, south, east, or west directions. The same is true for a cow next to the lake --- the cow can only extract a bucket of water from the lake if she is immediately adjacent to the lake. Similarly, a cow can only throw a bucket of water on the barn if she is immediately adjacent to the barn.
Please help determine the minimum number of '.' squares that should be occupied by cows to form a successful bucket brigade.
A cow cannot be placed on the square containing the large rock, and the barn and lake are guaranteed not to be immediately adjacent to each-other.
INPUT FORMAT (file buckets.in):
The input file contains 10 rows each with 10 characters, describing the layout of the farm.
OUTPUT FORMAT (file buckets.out):
Output a single integer giving the minimum number of cows needed to form a viable bucket brigade.
SAMPLE INPUT:
.......... .......... .......... ..B....... .......... .....R.... .......... .......... .....L.... ..........
SAMPLE OUTPUT:
7
In this example, here is one possible solution, which involves the optimal number of cows (7):
.......... .......... .......... ..B....... ..C....... ..CC.R.... ...CCC.... .....C.... .....L.... ..........
Problem credits: Brian Dean
中文版
農場上起火了，奶牛們正在緊急趕去滅火！
農場可以用一個像這樣的10×1010×10的字符方陣來描述：
.......... .......... .......... ..B....... .......... .....R.... .......... .......... .....L.... ..........
字符'B'表示正著火的牛棚。字符'L'表示一個湖，而字符'R'表示農場上的一塊巨大巖石。
奶牛們想要沿著一條湖到牛棚之間的路徑組成一條“水桶傳遞隊列”，這樣她們就可以沿著這條路徑傳遞水桶來幫助滅火。當兩頭奶牛在東南西北四個方向上相鄰時水桶可以在她們之間傳遞。這對于湖邊的奶牛也是對的——奶牛只能在緊挨著湖的時候才能用水桶從湖里取水。類似地，奶牛只能在緊挨著牛棚的時候才能用水去滅牛棚的火。
請幫助求出奶牛們為了組成這樣的“水桶傳遞隊列”需要占據的'.'格子的最小數量。
奶牛不能站在巖石所在的方格之內，此外保證牛棚和湖不是相鄰的。
輸入格式（文件名：buckets.in）：
輸入包含10行，每行10個字符，描述這個農場的布局。輸入保證圖案中恰有一個字符'B'、一個字符'L'以及一個字符'R'。
輸出格式（文件名：buckets.out）：
輸出一個整數，為組成一條可行的水桶傳遞隊列所需要的奶牛的最小數量。
輸入樣例：
.......... .......... .......... ..B....... .......... .....R.... .......... .......... .....L.... ..........
輸出樣例：
7
在這個例子中，以下是一個可行的方案，使用了最小數量的奶牛（7）：
.......... .......... .......... ..B....... ..C....... ..CC.R.... ...CCC.... .....C.... .....L.... ..........
供題：Brian Dean
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